Re: [PATCH 1/5] BIOS changes for configuring irq0->inti2 override (v4)

Sebastian Herbszt
2009-06-11T20:51:46Z

Beth Kon wrote:
> These patches resolve the irq0->inti2 override issue, and get the hpet working
> on kvm.
>
> Override and HPET changes are sent as a series because HPET depends on the
> override. Win2k8 expects the HPET interrupt on inti2, regardless of whether
> an override exists in the BIOS. And the HPET spec states that in legacy mode,
> timer interrupt is on inti2.
>
> The irq0->inti2 override will always be used unless the kernel cannot do irq
> routing (i.e., compatibility with old kernels). So if the kernel is capable,
> userspace sets up irq0->inti2 via the irq routing interface, and adds the
> irq0->inti2 override to the MADT interrupt source override table,
> and the mp table (for the no-acpi case).
>
> Changes from v3:
>
> - changes based on comments from Avi and Gleb.
> - corrected legacy enable/disable for in-kernel PIT. The code now best
> approximates a multiplexer that disables PIT interrupts when HPET is
> in legacy mode (as described by HPET spec). Any changes to the PIT that
> may occur while HPET is operating in legacy mode are saved, so if
> HPET leaves legacy mode, the PIT is just reenabled, with mode set
> to whatever the last setting from guest was. Legacy mode is disabled
> at least during crash and shutdown (in Linux), so this needs to be
> handled properly.
>
>
> ---
> kvm/bios/rombios32.c | 60 ++++++++++++++++++++++++++++++++++++-------------
> 1 files changed, 44 insertions(+), 16 deletions(-)

What about the mptable entry count?
Think it would need something like

#ifdef BX_QEMU
if (irq0_override)
putle16(&q, smp_cpus + 17); /* entry count */
else
putle16(&q, smp_cpus + 18); /* entry count */
#else
putle16(&q, smp_cpus + 18); /* entry count */
#endif

Your patch "Fix non-ACPI Timer Interrupt Routing - v3" [1] included such a change.

[1] http://lists.gnu.org/archive/html/qemu-devel/2009-04/msg01396.html

- Sebastian